Resonators find many applications, one of which is the measurement of fluid properties. In some environments, such as in an instrument package mounted in close proximity to an oil or gas well-drilling tool, viscometers are subjected to large and variable forces exerted on the structure by which the resonator is mounted in its casing. These forces have the potential to affect the accuracy and/or reproducibility of the measured fluid properties. A further feature of the oil drilling environment is extremely high pressures, which have the potential to distort or collapse any structure that surrounds a void. This requires that any void in a measurement device, have a passage for fluid entry, to balance the force on the walls defining the void, or else be surrounded by a robust pressure vessel.
Separately, tuning forks are frequently employed as resonators used to measure fluid properties. A conventional tuning fork 10, an example of which is shown in FIG. 1, consists of two tines 12, typically of flat or circular cross section, that are attached to a cross beam 14, which is attached to a mounting base structure 16. The cross beam is frequently integrated with the two tines so as to resemble a single U shaped element. If such a tuning fork is excited at its resonant frequency and immersed in a fluid, it will both move fluid through the transverse motion of its tines, and shear the fluid at the surface that is parallel to the motion of the tines. The resonant frequency of the vibration due to the motion of the tine surfaces that are perpendicular to the direction of tine motion will be most strongly affected by the density of the fluid these surfaces push against. But the damping of the vibration due to the motion of the tine surfaces that are parallel to the direction of tine motion will be most strongly affected by the viscosity of the fluid being sheared by these surfaces.